Multiband Camera Pupil-Plane Filter Alignment
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Solution Overview
Problem
Existing multiband camera systems face difficulties in aligning the color filter array with the optical system when it is disposed near the object lens rather than directly in front of the detector array, affecting the capture of multiband two-dimensional spectral images.
Innovation Solution
A multiband camera system with a band-pass filter positioned at the pupil of the optical system, featuring a microlens array and a photoelectric conversion element with pixels aligned to capture light fluxes through the band-pass filter, and a measurement unit to determine spectral intensity, adhering to specific pitch and alignment criteria to ensure accurate image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the color filter array is disposed in the neighborhood of the object lens at a distance from the microlens array, then the multiband camera can capture wavelength bands divided into four or more bands, but it becomes difficult to align the color filter array with the optical system
Solution Approach 1:
The patent introduces a band-pass filter as an intermediary element positioned at the pupil plane of the optical system. This filter acts as a mediator between the object lens and the microlens array, enabling wavelength band division while maintaining proper alignment with the optical system. The band-pass filter's position at the pupil plane allows it to function as a spatial filter that divides the light into multiple wavelength bands without compromising alignment precision.
Solution Approach 2:
The patent transitions from a one-dimensional arrangement (color filter array directly in front of detector) to a multi-dimensional configuration by positioning the band-pass filter at the pupil plane in the optical path. This spatial repositioning in a different dimension (the pupil plane rather than the image plane) enables the system to achieve both wavelength band division and proper alignment simultaneously.
2Measurement precision
If the band-pass filter is disposed inside the imaging optical system at the pupil position, then accurate spectral intensity measurement can be achieved, but the optical system becomes more complex
Solution Approach 1:
The band-pass filter positioned at the pupil plane serves multiple functions simultaneously: it acts as a wavelength selector, a spatial filter, and an alignment reference. By consolidating these functions into a single element at a critical position in the optical path, the system achieves accurate spectral measurement without proportionally increasing complexity.
Solution Approach 2:
The band-pass filter performs preliminary wavelength selection and spatial filtering of the light before it reaches the microlens array and detector. This preliminary action at the pupil plane simplifies subsequent processing and ensures that only the desired wavelength bands are processed further, improving measurement accuracy while managing system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the capture of a multiband two-dimensional spectral image in a single shot, overcoming alignment challenges and ensuring precise spectral intensity measurement across divided wavelength bands.
Implementation Method 1
a band-pass filter that is disposed in a position of a pupil of an optical system and has four or more optical filters for respectively transmitting the wavelength bands divided into four or more bands
Implementation Method 2
a microlens array having two-dimensionally arrayed positive microlenses... which guides a flux of light transmitted through the band-pass filter to the plurality of two-dimensionally arrayed pixels
Implementation Method 3
a photoelectric conversion element that is disposed in the vicinity of a focal point of the microlens array and is disposed in or proximal to a conjugate position with the band-pass filter, and includes a plurality of two-dimensionally arrayed pixels on which is incident a flux of light transmitted through the band-pass filter
Data Source
AI summary
A multiband camera comprises: a band-pass filter having four or more optical filters; a microlens array having arrayed microlenses; a photoelectric conversion element including a plurality of pixels; and a measurement unit for measuring spectral intensity. The multiband camera satisfies the expression below, where Pl is a pitch between the microlenses, Ps is a pitch between the pixels, n is a number of pixels corresponding to one microlens, u is an effective dimension in a prescribed direction of the pixels, t is a dimension in the prescribed direction of a real image that the band-pass filter forms on a plurality of two-dimensionally arrayed pixels, Na is a number of microlenses arrayed in the prescribed direction, L is a distance from an exit pupil to the microlens, and f is a focal length of the microlens.[Expression14](1-fL)nPs-3Ps-u-tNa≤Pl≤(1-fL)nPs+3Ps-u-tNa